The present application claims priority to Application No. 102 05 541.6, filed in the Federal Republic of Germany on Feb. 8, 2002, which is expressly incorporated herein in its entirety by reference thereto.
The present invention relates to a clamping mechanism for locating and clamping sheet metal workpieces.
European Published Patent Application No. 0 909 607 describes a clamping mechanism for the clamping of sheet metal parts. Such clamping mechanisms are used, for example, for the precisely positioned fixing of two sheet metal parts during spot welding, especially in the process of manufacturing vehicle bodies. The clamping mechanism includes two contact surfaces, between which the sheet metal parts are: clamped. The first contact surface is part of a carrier plate, which is rigidly bolted to a fixed support element, which is fixed, for example to a clamping frame or a base plate. The second contact surface is situated on a clamping jaw, which is swivel-mounted on a carrier member connected to the carrier plate. By swivelling the clamping jaw, the clamping mechanism can be brought from a clamping position, in which the contact surfaces on carrier plate and clamping jaw are situated directly opposite one another, clamping the sheet metal parts that are to be joined between the two contact surfaces, into an open position, in which the contact area of the clamping jaw is distanced from the contact area of the carrier plate, so that the sheet metal parts can be removed from the clamping mechanism. The carrier member, to which the swivelling clamping jaw is fixed, is bolted to the carrier plate, so that the relative position of the clamping jaw in relation to the carrier plate is invariably fixed. When converting the clamping mechanism, the relative position of the corresponding contact surfaces therefore remains unchanged, so that no time-consuming adjustment of the clamping jaw in relation to the carrier plate is necessary. On the other hand, the clamping mechanism permits adjustment of the overall unit arranged on the carrier plate in relation to the support element (and hence in relation to the clamping frame or the base plate). The through-holes, through which the connecting bolts are passed for attaching the carrier plate to the support element, have a diameter larger than that of the bolts, so that the carrier plate can be displaced in relation to the support element in a plane perpendicular to the bolting direction. For fixing the carrier plate in the desired position relative to the support element, shims are provided, which are inserted between carrier plate and support element.
The clamping mechanism described in European Published Patent Application No. 0 909 607 thereby permits a joint adjustment of a plurality of contact areas situated a fixed distance from one another, precise adjustment being effected by displacement of the carrier plate, carrying the contact areas, in relation to the support element. The adjustment by shims which are inserted between opposing stop surfaces on carrier plate and support element has the disadvantage, however, that these stop surfaces must be machined with great accuracy in order to achieve a reproducible adjustment, which is associated with high machining costs. Furthermore, a number of individual components, which have to be produced with great accuracy, are needed for such an adjustment, which makes the adjustment expensive. Finally, the contact surface in the area where the carrier plate rests on the support element is relatively small, which reduces the stability of the clamping mechanism.
It is an object of the present invention to provide a clamping mechanism which avoids the forgoing disadvantages.
The above and other beneficial objects of the present invention are achieved by providing a clamping mechanism as described herein.
According to one aspect of the present invention, the carrier plate is attached to the support element by an intermediate plate arranged between carrier plate and support element. The intermediate plate and the carrier plate are provided with a first set of very precisely positioned holes for a first set of locating pins, by which the intermediate plate is precisely positioned in relation to the carrier plate. In addition, the intermediate plate and the support element are provided with a second set of very precisely positioned holes for a second set of locating pins, by which the intermediate plate is precisely positioned in relation to the support element. The locating pin holes on support element and carrier plate are arranged in a firmly predefined standard position, so that different support elements and carrier plates have an identical alignment of the holes. The position (or the offset) of the holes on the intermediate plate, on the other hand, is adapted to suit the actual application: if the carrier platexe2x80x94due to wear, for example, or a geometric variation in the body parts to be joinedxe2x80x94is to be offset in relation to the support element, the intermediate plate originally provided between carrier plate and support element is replaced by a modified intermediate plate, the hole pattern of which has the required offset in relation to the hole pattern of the original intermediate plate. The carrier plate may thus be displaced quickly, easily and with high, reproducible accuracy in relation to the support element without individual modification or adjustment of the stop surfaces. The assembly including carrier plate, intermediate plate and support element aligned by the locating pins is located by fixing bolts.
The use of individually perforated intermediate plates means that, in contrast to the conventional clamping mechanism, the clamping mechanism according to the present invention may dispense with the use of shims, thereby reducing the number of individual components needed for adjustment of the clamping mechanism.
Furthermore, manufacture of the intermediate plates and carrier plates may be rendered very simple and cost-effective if these parts are cut out from plate material of the required thickness, by laser cutting, for example. The blanks cut in this manner need not be subjected to further machining in their opposing contact areas (apart from the introduction of holes or threads and any deburring of the edges that might be necessary, depending on the method of cutting used). In this, manner, considerable cost advantages may be achieved in comparison to the manufacture of the conventional clamping mechanisms, particularly since the high-precision machining of the contact surfaces between carrier plate and support element may no longer be necessary.
The carrier plate may be formed in two pieces and may include a body to be connected to the support element and a clamping element bolted to the body and carrying the first contact area. Shims may be inserted between carrier plate and clamping element, in order to adjust the position of the contact area on the carrier plate to the position of the contact area on the clamping jaw. A facility for individual adjustment of the clamping area may be advisable where a plurality of different contact areas are arranged on one carrier plate, which in the course of an initial adjustment of the clamping mechanism need to be individually adjusted to the areas of the sheet metal parts arranged opposite them.
The clamping mechanism according to the present invention may be suitable for clamping in the manufacture of prototype and pre-production vehicles. Its facility for rapid, cost-effective manufacture may provide that this clamping mechanism may be inexpensively adapted to any change in the components to be joined, in the case of minor modifications, by shifting an existing carrier plate relative to the support structure using an intermediate plate with a modified hole pattern, or in the case of more major modifications by cutting out a new carrier plate, which is then bolted onto the support structure using an existing intermediate plate. In this case, the carrier plate may be designed in one piece, in order to save the additional cost associated with the manufacture of a connecting area between body and clamping element. In this application, furthermore, the clamping jaw may be closed and opened manually, thereby avoiding the costs of an expensive, automated control mechanism.
The present invention will be explained in more detail below with reference to exemplary embodiments represented in the Figures.